1. Field of the Invention
The present invention relates generally to radio communication systems. More specifically, a system and method for small built-in antennas that can be incorporated into short range communication devices such as cordless headsets are disclosed.
2. Description of Related Art
It is often desirable to provide wireless communication rather than wired communication using cables between related pairs of devices separated by a short distance. Devices that communicate using cables often require the devices to be located in close proximity to each other as dictated in part by the length of the cables. In contrast, wireless communication decreases the amount of cabling between devices and thus increases the ease of use and convenience for the user, is more aesthetic, and may provide added safety. With wireless communication, the distance between the related devices is generally only limited by the limits of the wireless signal transmission and receive systems. Examples of related pairs of devices include a cordless headset on the one hand and a telephone, computer, television, VCR, DVD player, video game player, stereo receiver, CD player, and MP3 player on the other hand. Other examples of related pairs of devices include a computer and its various external devices such as a monitor, printer, keyboard, mouse, telephone and speakers, for example.
A cordless headset requires an internal antenna to permit a radio in the headset to communicate with a radio in a corresponding base unit. In general, it is desirable to minimize the size of the headset so as to provide a headset that is as discrete as practicable. The volume within the headset is governed by industrial design and may place restrictions on both the size of the antenna and the size of the ground plane. However, the dimensions of the antenna residing within the headset are dictated by the wavelengths of the signals that the antenna is to receive and transmit as well as the form of the antenna. Thus, the antenna and the headset are designed with mutual considerations in order to accommodate the antenna within the headset.
Many types of antenna technologies may be chosen for the internal antenna of the headset. The selection depends upon the size and shape of the headset volume into which the antenna must fit and the system electrical and performance requirements of the antenna. An Inverted F Antenna (IFA) is often utilized for headsets operating in the 1900 MHz radio frequency band. However, the need for the IFA to occupy the centerline of the headset undesirably restricts placement of various switches and/or buttons of the headset. In addition, the IFA has a relatively high profile, e.g., approximately 5 mm. Thus, the dimensions and the positioning of the IFA within the headset negatively impacts the industrial design of the headset by increasing the height of and restricting the placement of switches and buttons on the headset.
To overcome the increased height and the restricted placement of switches and buttons, some headsets utilize a quarter-wave dipole antenna, e.g., a 1.6″ single wire housed within a boom of the headset. However, the quarter-wave dipole antenna increases the assembly cost and introduces interference to wires of the microphone housed within the boom due to the proximity of the microphone wires to the antenna, resulting in performance degradation.
Thus, what is needed is an antenna for use in a communication headset that meets required RF performance without or with minimized performance degradation resulting from interference with the microphone wires. The antenna is preferably low profile and configured to allow better placement of controls switches and/or buttons of the headset. Ideally, the antenna is also cost-effective to manufacture and to assemble.